The present invention relates to a memory including dummy cells.
In a one-chip memory where a number of memory cells are arranged on a single substrate in a batch process, when a signal read out of the memory cell is small, a dummy cell is used to sense the small signal at a high signal-to-noise ratio.
Heretofore, in the memory of this type, dummy cells have been provided one for each of a pair of data lines connected to each preamplifier.
A major noise appearing on the data lines is caused by electrostatic capacitances dependent on overlapping areas of word lines and the data lines at the crosspoints thereof. When the memory cells of different structure are included, the electrostatic capacitances differ between the data lines because of the layout of the memory cells and the misalignment of a mask during a manufacturing process. Accordingly, where the dummy cells are arranged one for each of the data lines as in the prior art memory, a memory cell having a different electrostatic capacitance than that of the dummy cell always exists and the noises on the pair data lines differ from each other resulting in the reduction of the signal-to-noise ratio.